Patent GB-1085907-A (GB)
Title: Improvements in vehicle steering gears
IPC: B62D5/087
Filed: 1964-11-27
Abstract: 1,085,907. Steering vehicles. ROBERT BOSCH G.m b.H Nov. 27, 1964 [Jan. 10, 1964]. No. 48211/64. Heading B7H. A power-assisted steering mechanism comprises a steering shaft 30 operable by the vehicle steering wheel and journalled at 31 in a shaft 25 having an extension 26 connected to the steering linkage. A toothed wheel 29 rotatably mounted on a shaft 33 meshes with teeth on the shaft 30 and with rack teeth on a power piston 23 which are also in mesh with gears 27 and 28 formed integrally with the shaft 25 so that rotation of the shaft 30 is transmitted to the steered wheels through gear 29, rack 23 and gears 27, 28. The shaft 33 is allowed limited pivotal movement about one end 34, its other end 35 operating a pressure fluid control system. Fluid from a reservoir 2 is supplied by a pump 1 through a pressure relief valve 55 to supply lines 5 and 6 and to an accumulator 3. The lines 5 and 6 lead to chambers 10, 10<SP>1</SP> which contain non-return valves 13, 131 loaded by springs 14, 141 which also load ball valves 16, 16<SP>1</SP> which are connected by stems 19, 19<SP>1</SP> with valves 20, 20<SP>1</SP>. The latter are located in chambers 18, 18<SP>1</SP> which are connected by passages 21, 21<SP>1</SP> to opposite ends of a cylinder 22 containing the rack piston 23. The chambers 18, 18<SP>1</SP> are separated from chambers 38, 38<SP>1</SP> by flexible diaphragms 39, 39<SP>1</SP> to which are attached metal discs 40, 40<SP>1</SP> through which are formed passages 41, 41<SP>1</SP> and which are acted upon by springs 42, 42<SP>1</SP>. Cylinders 37, 37<SP>1</SP> extend into the chambers 38, 381 and are slidable axially, being urged by springs 51, 51<SP>1</SP> towards a middle, neutral position, in which they bear against the spherical free end 35 of the shaft 33 with a small amount of play between their flanged ends and a shoulder formed in the valve casing. When the steering shaft 30 is rotated, the rack piston 23 is moved by the gear 29, during which operation the shaft 33 pivots about its end 34, thereby moving one of the cylinders 37, 371 into the chamber 38 or 38<SP>1</SP>, increasing the pressure therein so that the diaphragm 39 or 39<SP>1</SP> moves so as to unseat the associated valve, say valve 16. Fluid from the line 5 then passes through chamber 10 and passage 21 to act upon piston 23, so assisting the steering movement, while fluid displaced from the opposite end of cylinder 22 flows through passage 21<SP>1</SP>. The pressure in chamber 18<SP>1</SP> increases so that the diaphragm 39<SP>1</SP> moves away from the valve end 20<SP>1</SP> allowing the displaced fluid to pass through aperture 41<SP>1</SP>, through cylinder 37<SP>1</SP> and passages 53 and 54 to reservoir. At the given angle of steer, the apparatus is balanced by the springs 14, 14<SP>1</SP>, 42, 42<SP>1</SP> and 51, 51<SP>1</SP> in an hydraulically neutral position again, and the straight ahead position is resumed by rotating the steering wheel in the opposite direction, setting up the opposite conditions. At a given position of the steering wheel, road shocks react through piston 23 against fluid locked in the chambers 10, although, in a modification, the ball valves 13, 13<SP>1</SP> may be dispensed with, in which case the hydraulic system acts to re-centre the wheels. The springs 51, 51<SP>1</SP> may also be omitted.